Aircraft manufacturers and operators utilize a continuously increasing number of electronic assemblies in aircraft. The electronic assemblies enhance comfort in the cabin on the one hand and aircraft safety on the other. The electronic assemblies generate waste heat and must be cooled in order to function reliably. The air-conditioning apparatus of conventional aircraft are unable, or only partly able, to meet these additional cooling demands.
In conventional aircraft the electronic devices are so designed that either they must be cooled only by free convection, that is, an air flow is established only through density differences of the air and thus cools the components of the electronic device which are heating up, or additional fans which generate forced convention are provided. Additional cooling capacity for cooling the electronic devices can be made available at present only by an air-conditioning system and with the use of corresponding, weight-increasing conduits.
As previously mentioned, cooling of electronic devices and their components may be effected by means of natural convection. For this purpose the components are designed correspondingly, or fin-like heat sinks, intended to ensure adequate cooling by means of a correspondingly large surface area, are attached thereto. Cooling of the electronic devices and their components is provided either through the already existing air-conditioning system, which is used, for example, for cooling the cabin of the aircraft, or an additional air-conditioning system is provided.
With the aforementioned methods the electronic devices and their components must be so constructed, as early as the design stage thereof, that they withstand the demanding thermal conditions in an aircraft by heat radiation or natural convection. To increase the heat transfer, fans which draw air from the surroundings may be used. With a high cabin temperature, this cooling is frequently insufficient to transport away the heat load generated by the electronic devices. A further disadvantage of these aforementioned methods is that the fan itself generates heat and the mere circulation of the air heats the installation space for the electronic devices, too. The aforementioned methods are unable to cope with larger heat loads of the kind which can be produced by future electronic devices with increased performance.
Cooling of the electronic devices with the aircraft air-conditioning system requires a large amount of space and is insufficiently flexible. The aircraft air-conditioning system has to cool the air provided for cooling the electronic devices. Air supply ducts must be installed in the aircraft from the aircraft air-conditioning system to the electronic devices to be cooled, together with air discharge duds from the electronic devices to be cooled to the aircraft air-conditioning system. Depending on the installation position of the electronics, for example, below the cockpit, if the electronic devices of the aircraft are arranged in that location, the installation of such air supply and discharge ducts can be complex and costly and, furthermore, can require installation space which consequently is not available for other functions. With such long air supply ducts, high thermal and pneumatic losses occur which must be compensated by correspondingly higher performance of the air-conditioning system. This results, inter alia, in the lack of flexibility of these methods. Furthermore, the space conditions prevailing in the aircraft fuselage oppose the use of the aircraft air-conditioning system for cooling the electronic device. In addition, the performance of an aircraft air-conditioning system will be unable to meet the future demands for cooling electronic devices.
DE 103 33 353 A1 discloses a system in which a plurality of electronic devices are cooled with air.